Controlled or sustained release dosage forms are well known in the prior art and make broad use of polymeric compositions to delay or control the release of a medicament or nutritional supplement. Controlled or sustained release dosage forms are desirable because they provide a single dosage application without overdosing the patient and deliver a medicament or nutritional supplement at an appropriate rate to provide the desired activity over periods of time of up to 24 hours. These dosage forms can be formulated into a variety of physical structures or forms, including tablets, lozenges, gelcaps, buccal patches, suspensions, solutions, gels, etc.
Polymer blends in sustained release compositions are known and used in the pharmaceutical industry because of the blend's versatility of being able to create different release profiles. Cellulose ethers are desirable polymers for use in sustained release compositions because they are derived from naturally occurring cellulose, and are free-flowing, readily compressible powders. Unfortunately, not all cellulose ethers provide a desirable release profile for compressed tablets.
Many approaches are disclosed in the prior art for creating blends with unique characteristics. Blending of hydroxypropylmethylcellulose (HPMC) with other polysaccharides is a common blending approach as seen in the prior art.
Two examples of this approach are disclosed in U.S. Pat. No. 4,389,393 that discloses HPMC and carboxymethylcellulose (CMC) blends and U.S. Pat. No. 4,756,911 that discloses HPMC and guar gum blends. Another blending approach is disclosed in U.S. Pat. No. 5,451,409 that blends hydroxypropylcellulose (HPC) with hydroxyethylcellulose (HEC) for use as sustained release pharmaceutical matrix compositions. U.S. Pat. No. 4,704,285 discloses the use of fine particle size HPC alone or blended with HPMC for sustained release applications; U.S. Pat. No. 4,259,314 also discloses the use of the blend of HPMC and HPC with both hygroscopic and non-hygroscopic materials.
Although many different approaches are disclosed in the prior art for creating blends of cellulose ethers, a need still exists in the pharmaceutical industry for having additional cellulose ether polymeric materials that would provide additional flexibility in sufficient release profiles that are stable yet economical for compressed tablets. In addition to providing the desired release rate profile, the polymeric composition should also provide required material properties to the dosage form for safe use and consistent manufacture.